Optic neuropathies are conditions that cause disease to the optic nerve, and can result in loss of visual acuity and/or visual field defects. An improved understanding of how these conditions affect the entire visual system is warranted, to better predict and/or restore the visual loss. In this article, we review visually-driven functional magnetic resonance imaging (fMRI) studies of optic neuropathies, including glaucoma and optic neuritis (ON); we also discuss traumatic optic neuropathy (TON). Optic (...) neuropathy-related vision loss results in fMRI deficit within the visual cortex, and is often strongly correlated with clinical severity measures. Using predominantly flickering checkerboard stimuli, glaucoma studies indicated retinotopic-specific cortical alteration with more prominent deficits in advanced than in early glaucoma. Some glaucoma studies indicate a reorganized visual cortex. ON studies have indicated that the impacted cortical areas are briefly hyperactive. For ON, brain deficits are greater in the acute stages of the disease, followed by (near) normalization of responses of the LGN, visual cortex, and the dorsal visual stream, but not the ventral extrastriate cortex. Visually-driven fMRI is sensitive, at least in ON, in discriminating patients from controls, as well as the affected eye from the fellow eye within patients. The use of a greater variety of stimuli beyond checkerboards (e.g., visual motion and object recognition) in recent ON studies is encouraging, and needs to continue to disentangle the results in terms of change over time. Finally, visually-driven fMRI has not yet been applied in TON, although preliminary efforts suggest it may be feasible. Future fMRI studies of optic neuropathies should consider using more complex visual stimuli, and inter-regional analysis methods including functional connectivity. We suggest that a more systematic longitudinal comparison of optic neuropathies with advanced fMRI would provide improved diagnostic and prognostic information. (shrink)

ObjectiveTo elucidate the clinical, radiologic characteristics of Leber’s hereditary optic neuropathy (LHON) associated with the other diseases.Materials and methodsClinical data were retrospectively collected from hospitalized patients with LHON associated with the other diseases at the Neuro-Ophthalmology Department at the Chinese People’s Liberation Army General Hospital (PLAGH) from December 2014 to October 2018.ResultsA total of 13 patients, 24 eyes (10 men and 3 women; mean age, 30.69 ± 12.76 years) with LHON mitochondrial DNA (mtDNA) mutations, were included in the cohort. (...) 14502(5)11778(4)11778 &11696(1)12811(1)11696(1)3460(1). One patient was positive for aquaporin-4 antibody (AQP4-Ab), and two were positive for myelin oligodendrocyte glycoprotein antibody (MOG-Ab). Three patients were associated with idiopathic optic neuritis (ON). Two patients were with compression optic neuropathy. Three patients were with the central nervous system (CNS) diseases. One patient was with proliferative diabetic retinopathy (PDR) and one with idiopathic orbital inflammatory syndrome (IOIS). At the onset, visual acuity (VA) in eighteen eyes was below 0.1, one eye was 0.5, five eyes were above 0.5, while VA in sixteen eyes was below a 0.1 outcome, three eyes experienced moderate vision loss. MRI images showed T2 lesions and enhancement in nine patients who received corticosteroids treatment; additional immune modulators treatment was performed on two patients. None of the patients had relapse during the follow-up time.ConclusionLeber’s hereditary optic neuropathy can be accompanied with multiple-related diseases, especially different subtypes of ON, which were also exhibited with IOIS and compression optic neuropathy for the first time in this cohort. This condition may be a distinct entity with an unusual clinical and therapeutic profile. (shrink)

Optic neuropathy refers to disease of the optic nerve and can result in loss of visual acuity and/or visual field defects. Combining findings from multiple fMRI modalities can offer valuable information for characterizing and managing optic neuropathies. In this article, we review a subset of resting-state functional magnetic resonance imaging (RS-fMRI) studies of optic neuropathies. We consider glaucoma, acute optic neuritis (ON), discuss traumatic optic neuropathy (TON), and explore consistency between findings from RS (...) and visually driven fMRI studies. Consistent with visually driven studies, glaucoma studies at rest also indicated reduced activation in the visual cortex and dorsal visual stream. RS-fMRI further reported varying levels of functional connectivity in the ventral stream depending on disease severity. ON patients show alterations within the visual cortex in both fMRI techniques. Particularly, higher-than-normal RS activity is observed in the acute phase and decreases as the disease progresses. A similar pattern is observed in the visual cortex of TON-like, open globe injury (OGI), patients. Additionally, visually driven and RS-fMRI studies of ON patients show recovery of brain activity in the visual cortex. RS-fMRI suggests recovery of signals in higher-tier visual areas MT and LOC as well. Finally, RS-fMRI has not yet been applied to TON, although reviewing OGI studies suggests that it is feasible. Future RS-fMRI studies of optic neuropathies could prioritize studying the fine scale RS activity of brain areas that visually driven studies have identified. We suggest that a more systematic longitudinal comparison of optic neuropathies with advanced fMRI would provide improved diagnostic and prognostic information. (shrink)

Myelin oligodendrocyte glycoprotein antibody-associated disease is an immune-mediated demyelinating disease of the central nervous system that is present in both adults and children. The most common clinical manifestations are optic neuritis, myelitis, acute disseminated encephalomyelitis, and brainstem syndrome. Cerebral cortical encephalitis is a rare clinical phenotype of myelin oligodendrocyte glycoprotein antibody-associated disease, which usually begins with seizures, headaches, and fever, and may be misdiagnosed as viral encephalitis in the early stages. Herein, we report two typical MOG antibody -positive (...) patients presenting with CCE, both of whom presented with headache, fever, seizures, and who recovered completely after immunotherapy. In addition, we performed a systematic review of the present literature from the perspectives of population characteristics, clinical symptoms, MRI abnormalities, treatments, and prognosis. Among the patients reported in 25 articles, 33 met our inclusion criteria, with the age of onset ranging from 4 to 52 years. Most of the patients had seizures, headache, fever, and unilateral cortical lesions on brain MRI. For acute CCE, 30 patients were treated with high-dose intravenous methylprednisolone, and the symptoms of most patients were completely relieved after immunotherapy. This study reported our experience and lessons learned in the diagnosis and treatment of MOG-Ab-positive CCE and provides a systematic review of the literature to analyse this rare clinical phenotype. (shrink)

Minkowski geometry is axiomatized in terms of the asymmetric binary relation of optical connectibility, using ten first-order axioms and the second-order continuity axiom. An axiom system in terms of the symmetric binary optical connection relation is also presented. The present development is much simpler than the corresponding work of Robb, upon which it is modeled.

Significantly, Berkeley, in his Essay Towards a New Theory of Vision, leveled a sustained attack on just this geometrical theory of distance perception. At first glance it may seem, as it did to Berkeley, that Descartes’ geometrical theory is produced by a simple error: namely, by the idea that a physiological optics provides an adequate description of the psychological processes of judging distances. In truth, this is the weakest of Berkeley’s objections to Descartes’ theory. Obviously we do not see the (...) angles and lines of convergence when we focus on a distant object, nor are we aware of having used any geometrical rules in judging distance. And Descartes never claimed this. (shrink)

_ Source: _Volume 29, Issue 1, pp 86 - 102 The aim of this paper is to give an overview of the place that Hobbes assigns to optics in the context of his classification of sciences and disciplinary boundaries. To do this, I will begin with an account of Hobbes’s conception of philosophy or science, and particularly his distinction between true and hypothetical knowledge. I will also show that in his demarcation between mathematics or geometry and natural philosophy Hobbes was (...) influenced by Galileo’s _Dialogue_. I then analyse the consequences of this distinction for optics, and conclude by clarifying its status among the scientific disciplines. (shrink)

_ Source: _Volume 29, Issue 1, pp 39 - 65 Since Euclid, optics has been considered a geometrical science, which Aristotle defines as a “mixed” mathematical science. Hobbes follows this tradition and clearly places optics among physical sciences. However, modern scholars point to a confusion between geometry and physics and do not seem to agree about the way Hobbes mixes both sciences. In this paper, I return to this alleged confusion and intend to emphasize the peculiarity of Hobbes’s geometrical optics. (...) This paper suggests that Hobbes’s conception of geometrical optics, as a mixed mathematical science, greatly differs from Descartes’s one, mainly because they do not share the same “mechanical conception of nature.” I will argue that Hobbes and Descartes also have in common the quest for a different kind of geometry for their optics, different from that of the Ancients. I will show that this departure is not recent since Hobbes’s approach is already evident in 1636, when he judges the demonstrations of his contemporary friends, Claude Mydorge and Walter Warner. Finally the paper broadly suggests what is noteworthy in Hobbes’s optics, that is, the importance of the idea of force in his mechanics, although he was not able to conceptualize it in other terms than “quickness.”. (shrink)

Seventeenth-century optics naturalizes the eye while estranging the mind from objects. A mere screen, on which rests a blurry array of light stains, the eye no longer furnishes the observer with genuine re-presentations of visible objects. The intellect is thus compelled to decipher flat images of no inherent epistemic value, accidental effects of a purely causal process, as vague, reversed reflections of wholly independent objects. Reflecting on and trespassing the boundaries between natural and artificial, orderly and disorderly, this optical paradox (...) is a Baroque phenomenon; and it is the origin of Descartes’ celebrated doubt---whether we know anything at all. (shrink)

Using the Q representation, we study the disagreement between quantum optical formalism and local realism and we show that the phenomenon of enhancement, first revealed by the local realist analysis, could receive a simple explanation if we use this particular version of the quantum formalism. Nevertheless, some fundamental difficulties remain.

Socrates, in the Republic, uses the symbol of a divided line to illustrate the distinction between the Visible and Intelligible Worlds, and between the kinds of perception appropriate to each. This paper will present a new hypothesis: that the proportions of the line are derived from optical theory. The construction of the Divided Line is described as follows: Socrates asks his interlocutors to represent the Visible and Intelligible Worlds by a line divided into two unequal segments. The ratio in which (...) the division is to be made is not specified, and it seems that any ratio is acceptable provided that one segment is longer than the other. Socrates then tells them to cut each part again according to the same ratio as the original division. After describing the division of the line thus into four parts, Socrates goes on to explain the philosophical significance of each part. For the purposes of this paper the following brief identification of each segment of the line will suffice. (shrink)

This book explores the interrelationships between optics, vision and perspective before the Classical Age, examining binocularity in particular. The author shows how binocular vision was one of the key juncture points between the three concepts and readers will see how important it is to understand the approach that scholars once took. In the Middle Ages and the Renaissance, the concept of Perspectiva – the Latin word for optics – encompassed many areas of enquiry that had been viewed since antiquity as (...) interconnected, but which a erwards were separated: optics was incorporated into the field of physics (i.e., physical and geometrical optics), vision came to be regarded as the sum of various psycho-physiological mechanisms involved in the way the eye operates (i.e., physiological optics and psychology of vision) and the word ‘perspective’ was reserved for the mathematical representation of the external world (i.e., linear perspective). The author shows how this division, which emerged as a result of the spread of the sciences in classical Europe, turns out to be an anachronism if we confront certain facts from the immediately preceding periods. It is essential to take into account the way medieval scholars posed the problem – which included all facets of the Latin word perspectiva – when exploring the events of this period. (shrink)

Socrates, in the Republic , uses the symbol of a divided line to illustrate the distinction between the Visible and Intelligible Worlds, and between the kinds of perception appropriate to each. This paper will present a new hypothesis: that the proportions of the line are derived from optical theory. The construction of the Divided Line is described as follows: Socrates asks his interlocutors to represent the Visible and Intelligible Worlds by a line divided into two unequal segments. The ratio in (...) which the division is to be made is not specified, and it seems that any ratio is acceptable provided that one segment is longer than the other. Socrates then tells them to cut each part again according to the same ratio as the original division. After describing the division of the line thus into four parts, Socrates goes on to explain the philosophical significance of each part. For the purposes of this paper the following brief identification of each segment of the line will suffice. (shrink)

The relativistic optics of the nondispersive media endowed with the metric gij(x) [Eq. (1.6)] and with a nonlinear connection [Eq. (1.2)] is studied. The d-connection [Eqs. (3.3)– (3.4)] relates the conformal and projective properties of the space- time. A post-Newtonian estimation for the metric gij(x) is also given. It is shown that the solar system tests impose a constraint [Eq. (4.20)] on a combination of the post- Newtonian parameters describing the model.

Descartes’ work on optics spanned his entire career and represents a fascinating area of inquiry from both the perspectives of the history of science and his systematic natural philosophy. The first of these entries offers a brief account of Descartes' seminal work in optics, the Dioptrique, often translated as the Optics or, more literally, as the Dioptrics. The second entry overview of Descartes’ understanding of light, his derivations of the two central laws of geometrical optics, and a sampling of the (...) optical phenomena he sought to explain. (shrink)

I argue that quantum optical experiments that purport to refute Bohr’s principle of complementarity fail in their aim. Some of these experiments try to refute complementarity by refuting the so called particle–wave duality relations, which evolved from the Wootters–Zurek reformulation of BPC. I therefore consider it important for my forgoing arguments to first recall the essential tenets of BPC, and to clearly separate BPC from WZPC, which I will argue is a direct contradiction of BPC. This leads to a need (...) to consider the meaning of particle–wave duality relations and to question their fundamental status. I further argue that particle and wave complementary concepts are on a different footing than other pairs of complementary concepts. (shrink)

The Dioptrique, often translated as the Optics or, more literally, as the Dioptrics is one of Descartes’ earliest works. Likely begun in the mid to late 1620’s, Descartes refers to it by name in a letter to Mersenne of 25 November 1630 III, 29). Its subject matter partially overlaps with Descartes’ more foundational project The World or Treatise on Light in which he offers a general mechanistic account of the universe including the formation, transmission, and reception of light. Although Galileo’s (...) condemnation by the Church prompted Descartes to abandon, in 1633, his plans for publishing The World, he continued in the ensuing years to vigorously pursue a number of scientific projects, including projects related to his work in optics. He was eventually persuaded to publish three essays highlighting some of his discoveries together with an introductory essay concerning “the method for rightly directing one’s reason and searching for truth in the sciences” . As one of those essays, Descartes’ Dioptrics finally appeared in print together with the Discourse on Method, the Meteorology and the Geometry in the summer of 1637 in a French language edition. It was republished in a Latin edition in 1644. The subject matter of the Dioptrics may be thought of as covering three main topics and is formally divided by Descartes into ten chapters or “discourses”. The first main topic concerns the nature of light and the laws of optics. In the first discourse, Descartes invites his readers to. (shrink)

Quantum optics does not give a local explanation of the coincidence counts in spatially separated photodetectors. This is the case for a wide variety of phenomena, including the anticorrelated counting rates in the two channels of a beam splitter, the coincident counting rates of the two “photons” in an atomic cascade, and the “antibunching” observed in resonance fluorescence.We propose a local realist theory that explains all of these data in a consistent manner. The theory uses a completely classical description of (...) the electromagnetic field, but with boundary conditions of the far field that are equivalent to assuming a real fluctuating, zero-point field. It is related to stochastic electrodynamics similarly to the way classical optics is related to classical electromagnetic theory.The quantitative aspects of the theory are developed sufficiently to show that there is agreement with all experiments performed till now. (shrink)

Ever since Big Data became a mot du jour across social fields, optical metaphors such as the microscope began to surface in popular discourse to describe and qualify its epistemological impact. While the persistence of optics seems to be at odds with the datafication of vision, this article suggests that the optical metaphor offers an opportunity to reflect about the material consequences of the modes of seeing and knowing that currently shape datafied worlds. Drawing on feminist new materialism, the article (...) investigates the optical metaphor as a material-discursive practice that actively constitutes the world, as metaphors imply modes of thinking, knowing and doing that have material enactions. Expanding visual culture theories, the notion of ‘optical unconscious’ is taken up to discuss the tensions between displacement and persistence of optics within datafied worlds, that is, how optical vision is displaced but also mobilised and repurposed by data-driven knowledge. In dialogue with feminist science and technology studies and speculative ethics, I suggest that the datafication of vision offers a chance to reconceptualize the sense of sight towards a sensorial engagement with Big Data premised on responsibility, care, and an ethics of unknowability. Within this framework, vision may be conceived differently, perhaps not only as enhancement and control, but as generator of new possibilities. Ultimately, the article proposes that the visual theories after which Big Data is being imagined matter not only for our understanding of Big Data's epistemic potential, but also for the possibility of shaping emerging data worlds. (shrink)

Leonardo's drawings of optical machinery have been used as evidence for the claim that Leonardo built machines to make concave mirrors with which he could project images. This paper argues that Leonardo's drawings cannot be used as evidence for this claim. It will be shown that Leonardo used the drawings to communicate with his patrons and craftsmen, to experiment on paper, to record trials with models, and to think about 'theoretical' problems in optics. At both the theoretical and the practical (...) level, Leonardo was only concerned with the burning properties of concave mirrors, not with their imaging properties. The paper will conclude that the drawings of optical machinery allowed Leonardo to differentiate himself from the ordinary mirror-makers in his workshop. The same drawings, however, also forced him to remain within the conceptual framework of perspectivist optics. (shrink)

In the previous article (Found. Phys. Lett. 16:325–341, 2003), we showed that a reciprocity of the Gauss sums is connected with the wave and particle complementary. In this article, we revise the previous investigation by considering a relation between the Gauss optics and the Gauss sum based upon the recent studies of the Weil representation for a finite group.

Typically developing 3-day-old newborns take significantly more forward steps on a moving treadmill belt than on a static belt. The current experiment examined whether projecting optic flows that specified forward motion onto the moving treadmill surface would further enhance forward stepping. Twenty newborns were supported on a moving treadmill without optic flow, with optic flow matching the treadmill’s direction and speed, with optic flow in the same direction but at a faster speed, and in a control (...) condition with an incoherent optic flow moving at the same speed as in the Congruent condition but in random directions. The results revealed no significant differences in the number or coordination of forward treadmill steps taken in each condition. However, the Faster condition generated significantly fewer leg pumping movements than the Random control condition. When highly aroused, newborns made significantly fewer single steps and significantly more parallel steps and pumping movements. We speculate the null findings may be a function of the high friction material that covered the treadmill surface. (shrink)

This volume contains essays that examine the optical works of Giambattista Della Porta, an Italian natural philosopher during the Scientific Revolution. Coverage also explores the science and technology of early modern optics. Della Porta's groundbreaking book, Magia Naturalis, includes a prototype of the camera. Yet, because of his obsession with magic, Della Porta's scientific achievements are often forgotten. As the contributors argue, his work inspired such great minds as Johanes Kepler and Francis Bacon. After reading this book, researchers, historians, and (...) students will have a better appreciation of this influential scientist. They will also gain a greater understanding of an important period in the history of optics. Readers will learn about Della Porta's experimental method, a process governed by the protocols, aims, and theoretical assumptions of natural magic. Coverage also discusses the material properties and limitations of optical technology in the early 17th century, based on a recently discovered Dutch spyglass. It also demonstrates how diagrams were instrumental in the discovery of the sine law of refraction. In addition, the book includes an in-depth analysis of previously untranslated Latin sources. This makes the material useful to historians of optics unfamiliar with the language. More than 70 illustrations complement the text. (shrink)

We propose an analogy between optical holography and neural behavior as a hypothesis about the physical mechanisms of neural reuse. Specifically, parameters in optical holography (frequency, amplitude, and phase of the reference beam) may provide useful analogues for understanding the role of different parameters in determining the behavior of neurons (e.g., frequency, amplitude, and phase of spiking behavior).

This book is a long-term history of optics, from early Greek theories of vision to the nineteenth-century victory of the wave theory of light. It is a clear and richly illustrated synthesis of a large amount of literature, and a reliable and efficient guide for anyone who wishes to enter this domain.

The screen is not a pre established object: it becomes a screen—and that screen—when it interacts with a group of elements and relates to a set of practices that produce it as a screen. In this process of becoming screen, a crucial step is played by the space in which the screen is located and where spectators gather. The confluence of screen and space changes our perception of both: the screen displays the situatedness of its action, and the space its (...) nature of medium. The landscape becomes a screenscape, in which individuals access images through which they negotiate with reality and others. Eventually, the insistence on becoming screen highlights the role of contingency and conjuncture in the process of mediation: screenscapes emerge according opportunities, conflicts, and potentialities. Hence a media archeology that, far from being linear and teleological, follows unpredicted paths and creates surprising links—a rhizomatic media archeology. (shrink)

The paper presents a preliminary estimation of the extent of dissemination of optical texts, ideas, and issues among the masters connected with the Prague faculty of arts in the late 14th and early 15th century. Investigation of this topic, so far rather neglected, is based chiefly on manuscript research. The paper brings evidence that perspectiva was taught in Prague at least since the 1370s. It suggests that investigation of Prague quodlibetal disputations (ca. 1390s – 1410s) and consideration of perspectivist authorities (...) employed in these texts can also shed some light on the issue. However, the paper is mainly devoted to the question on the mechanism of vision disputed by Bohemian arts master John of Borotín (Iohannes de Borotin, 1378 – after 1458) in the quodlibet organised by John Hus in 1411. It is suggested that the single extant exemplar of the question (preserved in the codex Prague, National Library, X.H.18) probably is Borotín’s autograph. The structure and sources of the question are analysed, with the conclusion being that Borotín proposes a compromise between intromission and extramission influenced by John Peckham’s Perspectiva communis. A critical edition of Borotín’s question is appended to the paper. / / / Please note this article is published with Brepols Publishers as a Gold Open Access article under a Creative Commons CC 4.0: BY-NC license. The article is also freely available on the website of Brepols Publishers under this same license. (shrink)

We have compared two different laser-induced optical light traps for their utility in moving organelles within living animal cells and walled fungal cells. The first trap employed a continuous wave neodymium-yttrium aluminum garnet laser at a wavelength of 1.06 micron. A second trap was constructed using a titanium-sapphire laser tunable from 700 to 1000 nm. With the latter trap we were able to achieve much stronger traps with less laser power and without damage to either mitochondria or spindles. Chromosomes and (...) nuclei were easily displaced, nucleoli were separated and moved far away from interphase nuclei, and Woronin bodies were removed from septa. In comparison, these manipulations were not possible with the Nd-YAG laser-induced trap. The optical force trap induced by the tunable titanium-sapphire laser should find wide application in experimental cell biology because the wavelength can be selected for maximization of force production and minimization of energy absorption which leads to unwanted cell damage. (shrink)

There has been much recent debate about the nature of the omnivoyant image that introduces Nicholas of Cusa’s De visione Dei. In this paper, I argue that Cusa’s concept of contraction and his ‘radical perspectivism’ lead us toward stretching the concept of omnivoyance beyond a simple dichotomy between a phenomenology of the image and a phenomenology of the icon. Instead of putting such emphasis on what is seen by the omnivoyant, we should think an omnivoyant optics starting from the material (...) milieu from which it sees. To this end, I define the concept of omnivoyance through the concept of the elemental. Using both the concept of an element derived from Presocratic Ionian philosophy and recent French and American continental philosophy, I put these discourses into conversation with Cusa in several ways: the way omnivoyance functions as a substratum of contracted seeing rather than as a transcendence, its operation as a pure frontality without objectifiable aspects, and the way in which omnivoyance implies not only a gaze that sees ‘all and each’ but also a plurality of modes of vision. To help us understand this enlarged concept of omnivoyance, I use the example of animal vision, particularly the gaze of the whale. With respect to cetacean vision, I deploy Melville’s metaphysical speculations in Moby Dick as our primary guide. (shrink)

This chapter discusses Thomas Hobbes's statements about the structure of philosophy and suggests that a focus on these reflections has led some scholars to understand Hobbes as an armchair speculative philosopher, both in his own natural‐philosophy endeavors and his well‐known criticisms of Robert Boyle and other experimental philosophers. Beyond Hobbes's statements about natural philosophy, it argues that a more complete understanding of his natural philosophy must also consider his practice of explaining in natural philosophy and optics. Hobbes divides all human (...) knowledge into two parts: scientia, and cognition. These two parts provide different levels of certainty to knowers. The chapter shows that explanations in optics and natural philosophy are ideally a mixture of appeals to everyday sense experience and Hobbes's own a priori geometry by providing two case studies: a case study from Hobbes's optics in De homine II and a case study of Hobbes's explanation of sense in De corpora XXV. (shrink)

In Mohist philosophy, the gnomon is a metaphor for the standard of valid arguments. This metaphor comes from the method of establishing due east and west by observing gnomon shadows at dusk and dawn. I argue that there is also an overlooked, implicit aspect of the gnomon metaphor that comes from its function of measuring the height of heaven indirectly through proportional calculation. The function of indirect measurement inspires a strategy of argumentation in Mohist ethics, which I call “analogical upscaling.” (...) Such an argument draws a parallel between small-scale and large-scale actions for the purpose of determining the Will of Heaven in a particular circumstance, just as the gnomon measures heaven’s physical height analogically. In the conclusion, I compare the epistemological status of light and shadow in the Mozi and Plato’s Republic. (shrink)

Neutron matter-wave optics provides the basis for new quantum experiments and a step towards applications of quantum phenomena. Most experiments have been performed with a perfect crystal neutron interferometer where widely separated coherent beams can be manipulated individually. Various geometric phases have been measured and their robustness against fluctuation effects has been proven, which may become a useful property for advanced quantum communication. Quantum contextuality for single particle systems shows that quantum correlations are to some extent more demanding than classical (...) ones. In this case entanglement between external and internal degrees of freedom offers new insights into basic laws of quantum physics. Non-contextuality hidden variable theories can be rejected by arguments based on the Kochen-Specker theorem. (shrink)